Currently running on 10-speed Campy Chorus groupset. Looking to replace rear derailleur and was wondering if anyone has tried the Campy Record 11 rear derailleur with the 13-29 10-speed cassette (I need all the help I can get on the climbs). I've done some searching here, and it sounds like it would work, but most seem to be running 11-25 or so. Also currently running on standard crankset, but looking to switch to a compact. If anyone has any experience with this, please provide your input!

I use a 12x29 for the really steep (20%+) but its an 11 speed cassette

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WW Velocipedist Gargantuan

My understanding is that an 11 speed short cage rear derailleur will shift 12-29 cassette with no issues. I also think that since indexing is done in shifter that 11 spd. derailleur is compatable with 10 spd cassette. I run 07 record 10 spd. 12-29 cassette (hybrid) with compact crankset and love it.

I have run 10-speed Record rear mech with 13-29 cassette and 50/34 cranks. No problem.

I have also run 11-speed SR rear mech with 12-29 cassette and 50/34 cranks. This also works no problem for 2010 rear mechs and later. Earlier 11-speed rear mechs need to be modified with a spare part to work with the 29-cog.

regarding the issue of Campy 10 speed shifters/cassettee with 11 speed rear der. Myself and others have done it with no modifications necessary. According to some there is a very, very slight bit more movement with the 11 spd rear der (compared to 10 spd) for the amount of cable being pulled by the shifter - but in the end it doesn't hurt and actually may help a bit.

Thanks so much for the replies so far. So it seems that the Record 11-speed rear mech will work with the 10-speed shifters and cassette. Is there only 1 size for the 11-speed rear mech as opposed to the short/medium/long for the 10-speed? I'm asking b/c for 13-29, it's suggested to use the medium cage, but for the Record 11, I don't see choices. Thanks.

I run a Super Record rear and front mech with a 13/29 cassette and Centaur levers. I have 50/34 on one bike and 48/33 on another. No issues at all.

also, what chain do you guys use with that setup? 10-speed, 11-speed, narrow?

10-speed

I forgot to add, when I first installed that 11 rear der I didn't like the look of the minimal clearance when running a 10 speed (5.9 mm) chain on that rear der, so I used very, very thin shims on both sides of the pulleys (about .2 mm thick each) along with running some replacement bolts with a modified length to compensate.

Maybe that modification isn't necessary but at the time I was installing the der it seemed reasonable to go that way.

Just because the shifter indexes doesn't mean that any RD will work the same. RD's have an actuation ratio that affects the amount of movment. The 11 speed RD has a slightly larger actuation ratio, but the difference is small and a little bit of overtravel is more tolerable than under travel.